Add type refinements for `Fp\Collection\filter`

[klimick]

use function Fp\Collection\filter;

/**
 * @psalm-return array<string, array>
 */
function getCollection(): array { return []; }

/**
 * @psalm-type Shape = array{name: string, postcode: int}
 * @psalm-assert-if-true Shape $shape
 */
function isValidShape(array $shape): bool
{
    return array_key_exists("name", $shape) &&
        array_key_exists("postcode", $shape) &&
        is_int($shape["postcode"]);
}

/** @psalm-trace $result */
$result = filter(
    getCollection(),
    fn(array $v) => isValidShape($v)
);

$result will be refined from array<string, array> to array<string, array{name: string, postcode: int}>